timegm

NAME

timegm, timelocal - inverses of gmtime and localtime

SYNOPSIS

 #include <time.h>
 
 time_t timelocal(struct tm *tm);
 
 time_t timegm(struct tm *tm);
 
 
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

timelocal(), timegm(): _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

The functions timelocal() and timegm() are the inverses of localtime(3) and gmtime(3).

CONFORMING TO

These functions are non-standard GNU extensions that are also present on the BSDs. Avoid their use; see NOTES.

NOTES

The timelocal() function is equivalent to the POSIX standard function mktime(3). There is no reason to ever use it.

For a portable version of timegm(), set the TZ environment variable to UTC, call mktime(3) and restore the value of TZ. Something like

 #include <time.h>
 #include <stdlib.h>
 
 time_t
 my_timegm(struct tm *tm)
 {
     time_t ret;
     char *tz;
 
     tz = getenv("TZ");
     setenv("TZ", "", 1);
     tzset();
     ret = mktime(tm);
     if (tz)
         setenv("TZ", tz, 1);
     else
         unsetenv("TZ");
     tzset();
     return ret;
 }
 

SEE ALSO

gmtime(3), localtime(3), mktime(3), tzset(3)

COLOPHON

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